Along with an improvement of performance of a semiconductor device, to reduce stray capacitance between interconnections in the semiconductor device and to increase an operation speed of the semiconductor device has been attempted. In order to reduce the stray capacitance between interconnections, a method of employing a material having a low dielectric constant as an interlayer dielectric formed between interconnections of the semiconductor devised is applied for example.
A silicon oxide film (SiO2 film) having a relative dielectric constant on the order of 4 has been employed in the above-mentioned interlayer dielectric. However, recently, an increase in an operating speed of a semiconductor device is sought, with the use of a fluorine-containing silicon oxide film (SiOF film) having a relative dielectric constant on the order of a range of 3 to 3.5.
However, there is a limit to reduce the relative dielectric constant of the above-mentioned SiOF film. To achieve a relative dielectric constant equal to or less than 3 is difficult.
Various candidates exist for a so-called low dielectric constant interlayer dielectric having a low relative dielectric constant. However, the requirements include not only having a low relative dielectric constant but also having such a mechanical strength that it can be applied in a semiconductor device. This is a reason why a fluorine-containing carbon film (CF film) has taken attention, having a sufficient mechanical strength, and also, having a relative dielectric constant which is on the order of 2 or may be further lowered. Attempts have been made to employ it as a low dielectric constant insulating film of a next generation. [Patent Document] WO99/35684
However, when the above-mentioned fluorine-containing carbon film is applied in a semiconductor device as an interlayer dielectric, a problem exists such that adhesion between the fluorine-containing carbon film and a foundation is low.
FIG. 1(A) through (C) shows an example in which a fluorine-containing carbon film is formed on a silicon nitride film (SiN film). When a fluorine-containing carbon film is applied in a semiconductor device as an interlayer dielectric, in many cases the fluorine-containing carbon film is formed on a SiN film acting as a cap layer of a Cu film which is an interconnection layer of the semiconductor device.
With reference to FIG. 1(A), a SiN film 101 is formed on a to-be-processed substrate not shown. Further, on the SiN film 101, a deposit layer 102, having a very small thickness in comparison to the SiN film 101, made of water, organic matter, natural oxide or such, is formed. The deposit film 102 may be formed as a result of the to-be-processed substrate having the SiN film formed thereon being exposed to the atmosphere for example.
Next, in FIG. 1(B), a fluorine-containing carbon film 103 is formed in a plasma CVD (chemical vapor deposition) method or such.
However, since the deposit layer 102 exists on the SiN layer 101 as mentioned above, there is a case where, as shown in FIG. 1(C), the fluorine-containing carbon film 103 peels from the SiN film 101 together with the deposit layer 102, or the fluorine-containing carbon film 103 peels from the deposit layer 102.
Further, even when such peeling does not occur immediately after the fluorine-containing carbon film 103 is formed, the fluorine-containing carbon film 103 may peel during a process, included in a semiconductor device manufacturing process, such as a thermal processing process applying a thermal stress, a CMP (chemical mechanical polishing) process applying shearing force, or such. To ensure sufficient adhesion between the foundation film and the fluorine-containing carbon film, satisfying such a requirement, is difficult.
In order to ensure the adhesion, a method exists of removing the above-mentioned deposit layer 102, for example, by means of spatter etching in a plasma processing apparatus for example. However, there is a problem that the above-mentioned SiN film 101 acting as a foundation film of the fluorine-containing carbon film may be damaged by ion impact of the spatter etching.
The present invention has an object to provide a fluorine-containing carbon film, solving the above-mentioned problem.
A specific problem to be solved by the present invention is to provide a fluorine-containing carbon film forming method in which no damage is caused to a foundation film of a fluorine-containing carbon film, and adhesion between the fluorine-containing carbon film and the function film is improved.